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[AMDGPU] Fix spurious NoAlias results #122309

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Merged
merged 4 commits into from
Jan 20, 2025
Merged

[AMDGPU] Fix spurious NoAlias results #122309

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d057782
[AMDGPU] Fix spurious NoAlias results
frasercrmck Jan 9, 2025
a6e37b2
remove attributes
frasercrmck Jan 9, 2025
57b2448
used identifiedobject
frasercrmck Jan 13, 2025
e18b903
swap checks
frasercrmck Jan 13, 2025
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8 changes: 6 additions & 2 deletions llvm/lib/Target/AMDGPU/AMDGPUAliasAnalysis.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -80,10 +80,14 @@ AliasResult AMDGPUAAResult::alias(const MemoryLocation &LocA,
} else if (const Argument *Arg = dyn_cast<Argument>(ObjA)) {
const Function *F = Arg->getParent();
switch (F->getCallingConv()) {
case CallingConv::AMDGPU_KERNEL:
case CallingConv::AMDGPU_KERNEL: {
// In the kernel function, kernel arguments won't alias to (local)
// variables in shared or private address space.
return AliasResult::NoAlias;
const auto *ObjB =
getUnderlyingObject(B.Ptr->stripPointerCastsForAliasAnalysis());
return ObjA != ObjB && isIdentifiedObject(ObjB) ? AliasResult::NoAlias
: AliasResult::MayAlias;
}
default:
// TODO: In the regular function, if that local variable in the
// location B is not captured, that argument pointer won't alias to it
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17 changes: 17 additions & 0 deletions llvm/test/CodeGen/AMDGPU/amdgpu-alias-analysis.ll
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Expand Up @@ -318,3 +318,20 @@ define void @test_9_9(ptr addrspace(9) %p, ptr addrspace(9) %p1) {
load i8, ptr addrspace(9) %p1
ret void
}

; CHECK-LABEL: Function: test_kernel_arg_local_ptr
; CHECK: MayAlias: i32 addrspace(3)* %arg, i32 addrspace(3)* %arg1
; CHECK: MayAlias: i32 addrspace(3)* %arg, i32* %arg2
; CHECK: MayAlias: i32 addrspace(3)* %arg1, i32* %arg2
define amdgpu_kernel void @test_kernel_arg_local_ptr(ptr addrspace(3) %arg) {
entry:
%load1 = load i32, ptr addrspace(3) %arg, align 4
%arg.plus.1 = getelementptr inbounds nuw i8, ptr addrspace(3) %arg, i64 1
%arg1 = getelementptr inbounds nuw i8, ptr addrspace(3) %arg.plus.1, i64 -1
%load2 = load i32, ptr addrspace(3) %arg1, align 4
%arg.plus.4 = getelementptr inbounds nuw i8, ptr addrspace(3) %arg, i64 4
%acast = addrspacecast ptr addrspace(3) %arg.plus.4 to ptr
%arg2 = getelementptr inbounds i8, ptr %acast, i64 -4
%load3 = load i32, ptr %arg2, align 4
ret void
}
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